One-DoF Robotic Design of Overconstrained Limbs with Energy-Efficient, Self-Collision-Free Motion

While it is expected to build robotic limbs with multiple degrees of freedom (DoF) inspired by nature, a single DoF design remains fundamental, providing benefits that include, but are not limited to, simplicity, robustness, cost-effectiveness, and efficiency. Mechanisms, especially those with multiple links and revolute joints connected in closed loops, play an enabling factor in introducing motion diversity for 1-DoF systems, which are usually constrained by self-collision during a full-cycle range of motion. This study presents a novel computational approach to designing one-degree-of-freedom (1-DoF) overconstrained robotic limbs for a desired spatial trajectory, while achieving energy-efficient, self-collision-free motion in full-cycle rotations. Firstly, we present the geometric optimization problem of linkage-based robotic limbs in a generalized formulation for self-collision-free design. Next, we formulate the spatial trajectory generation problem with the overconstrained linkages by optimizing the similarity and dynamic-related metrics. We further optimize the geometric shape of the overconstrained linkage to ensure smooth and collision-free motion driven by a single actuator. We validated our proposed method through various experiments, including personalized automata and bio-inspired hexapod robots. The resulting hexapod robot, featuring overconstrained robotic limbs, demonstrated outstanding energy efficiency during forward walking.

Overconstrained Robotic Limb with Energy-Efficient, Omni-directional Locomotion

This paper studies the design, modeling, and control of a novel quadruped, featuring overconstrained robotic limbs employing the Bennett linkage for motion and power transmission. The modular limb design allows the robot to morph into reptile- or mammal-inspired forms. In contrast to the prevailing focus on planar limbs, this research delves into the classical overconstrained linkages, which have strong theoretical foundations in advanced kinematics but limited engineering applications. The study showcases the morphological superiority of overconstrained robotic limbs that can transform into planar or spherical limbs, exemplifying the Bennett linkage. By conducting kinematic and dynamic modeling, we apply model predictive control to simulate a range of locomotion tasks, revealing that overconstrained limbs outperform planar designs in omni-directional tasks like forward trotting, lateral trotting, and turning on the spot when considering foothold distances. These findings highlight the biological distinctions in limb design between reptiles and mammals and represent the first documented instance of overconstrained robotic limbs outperforming planar designs in dynamic locomotion.